1. The Field of the Invention
The present invention relates generally to fittings and couplers for use with pipes and hoses. More particularly, the present invention relates to reusable pipe union assemblies which allow two pipes to be repeatedly joined together and released from a sealing engagement and which automatically checks the flow of fluid when the two pipes are released from the sealing engagement even under high temperature conditions.
2. The Background Art
In many areas of modern industry, there is an urgent need for devices which allow two pipes are to be repeatedly joined together while allowing for easy separation of the pipes. This need is especially urgent where the pipes subjected to extreme pressure and/or temperature conditions, including severe changes in temperature, i.e., thermal cycling. The chemical, cryogenic, petroleum, and composite materials fabrication fields are just some examples of industries having such needs.
Although many different devices have been developed in the prior art for joining pipes, such devices often require cumbersome tightening by unwieldy tools if very high pressures and/or high or low temperatures are involved. The various devices found in the prior art may be called Connectors, fittings, unions, couplings, joints, or some other name, but they all serve the same function of joining two pipes. Furthermore, not only are many of these prior art devices unsuitable in some applications, most also pose a safety threat to the operating mechanic assigned to loosen the connective fitting when high pressure is involved.
One of the most common methods of joining two pipes involves a flange joint. Use of the common "flange method" of joining two pipes has several disadvantages. First, it is generally cumbersome and quite difficult to join two pipes in this way, since many bolts and nuts are often required. It is important that all of the bolts be tightened equally. It will be appreciated that properly threading and tightening all the bolts and nuts on a flange joint can be a cumbersome task. The amount of time required to assemble or disassemble a flange joint can be a serious disadvantage in many applications.
Other disadvantages of the flange joint include the difficulty of disassembly because of the possibility of corrosion and aging of the flanges and ring gasket as well as the number of bolts and nuts which must be dealt with. Also, flange joints are subject to leakage when extremely cold, or extremely hot, fluid is introduced into the joint causing thermal contraction or expansion. Furthermore, repeated thermal expansion will often cause the joint to loosen and leak.
Also, in addition to the difficulty accompanying disassembly of the common flange joint, the person disassembling the flange joint is exposed to potential harm if any residual pressure remains within the system to which the pipes were connected. As a result, personal injury may occur during disassembly of a common flange joint because the flange joint does not provide any way of releasing residual pressure before being disassembled. If a method for releasing residual pressure is not provided, the person disassembling the joint faces the hazardous possibility that the joint will rapidly separate and spray its contents on the person during the disassembly procedure.
In an effort to overcome some of the above-mentioned difficulties, various devices have been suggested for use as easily assembled and/or reusable, pipe connectors. Among such pipe connectors which have-been developed is one known as a GRAYLOC.RTM. connector. While the GRAYLOC.RTM. connector is an improvement over the common flange joint, it is still relatively difficult to assemble and disassemble, since several bolts and nuts are still required by the clamp structure of the connector. Moreover, there is no assurance that a joint assembled at room temperature will remain secure when exposed to thermal cycling at high and low temperatures. Further, the seal ring may need to be replaced even after a single assembly procedure because of permanent deformation damage. The GRAYLOC.RTM. connector also provides little more protection to the person disassembling the joint from hazardous residual pressure than does the common flange joint.
Another common method of joining two pipes is known as the hammer union. In a hammer union, a first portion of the connector is provided with male pipe threads on its outer surface with its inner diameter being provided with a smooth sloping tapered surface oriented at an angle. A second portion of the connector is provided with a sloping tapered surface to complement that of the sloping tapered surface on the first portion.
The two tapered surfaces are mated together and an external rotating sleeve, with female threads, is slipped over the second portion of the pipe and threaded onto the male threads provided on the first portion of the connector. The external rotating sleeve, which is provided with ridges extending perpendicularly from its external circumference, is struck with a hammer in order to tighten the joint as much as possible. Thus, the name "hammer union."
The hammer union presents many of the same difficulties that are inherent in the "flange method" of joining two pipes, e.g., difficult disassembly, frequent inability to reuse the connector, and no protection from residual pressure remaining in the connector during disassembly.
One example of an attempt to provide a more easily assembled and disassembled pipe connector is known as a HANSEN.RTM. coupling. While the HANSEN.RTM. coupling has some advantages over other unions, the sealing function is provided by a flexible, rubber-like O-ring gasket which is unsuitable for use under extreme temperature or pressure conditions.
Another pipe connector which is an attempt to provide a more easily assembled and disassembled pipe union is known as a KAMLOK.TM. connector. The sealing function of the KAMLOK.TM. connector is provided by a gasket of rubber-like material. Thus, as with the HANSEN.RTM. coupling, the use of a flexible gasket seal makes this connector unsuitable for use in high temperature or high pressure applications.
An improvement over the above mentioned devices is found in Canadian Patent No. 1,026,791, issued to Krywitsky. The pipe fittings disclosed in the Krywitsky patent are an improvement over the HANSEN.RTM. coupling and the KAMLOK.TM. connector in that the sealing function is provided by a metal-to-metal interface which allows higher temperatures and pressures to be contained within the fitting than is possible when flexible, rubber-like gaskets are used.
The fitting disclosed in the Krywitsky patent uses tubular members which are provided with annular recesses which are defined by relatively thin and flexible lips which serve to carry out the sealing function. Protrusions are forced into the recesses which flex according to the degree of penetration of the protrusions. Furthermore, as the internal pressure of the fitting increases or decreases, the lips flex somewhat helping to maintain the sealing contact against the protrusion.
Use of the arrangement disclosed in the Krywitsky patent allows the pipe fitting to be used in applications involving either a constant high or low temperature, since the seal is formed by metal-to-metal contact. However, several difficulties are inherent in the design disclosed in the Krywitsky patent.
First, because the lips of the metallic sealing ring are relatively flexible, the maximum pressure which may be reliably contained under some circumstances is limited to about 40 pounds per square inch ("psi").
Second, the fitting of the Krywitsky patent may become difficult to disassemble if the fitting lips "seize" onto the protrusion where the protrusion has been allowed to penetrate into the recess too far. Such excessive penetration may be necessary to stop leaking at pressures near the maximum allowed for the device.
Third, the sealing structures of the device of the Krywitsky patent may fail or be subject to damage due to fatigue caused by the flexing of the annular lips.
Fourth, as the annular lips flex, the contact area between the protrusion and the lips generally decreases. As the protrusion is forced deeper between the annular lips, the contact area diminishes to a very thin line around the protrusion. Once the contact area has been reduced to such a "point contact," failure of the device may easily occur.
Fifth, as the sealing ring wears because of normal use, the protrusions may be allowed to completely penetrate to the bottom of the recesses while still not providing a sufficient seal to stop leaking.
Sixth, because the sealing components may be easily damaged and subject to rapid wear, the reusability of the pipe fitting is uncertain from one use to the next.
Seventh, it is nearly always necessary to use tools to assemble or disassemble the fitting because of the pressure required to force the protrusion between the annular lips. The fact that tools must always be used decreases the usefulness of the connector. In many applications involving only moderate pressure, it would be very desirable to provide a connector which requires only hand tightening.
Thus, the pipe connector disclosed in the Krywitsky patent is useful over only a limited range of pressures, and questions of reliability arise after the fitting has been properly used only a few times, or improperly used (e.g., over-tightened), even once.
Still another need which has been unmet in the art is to provide a pipe connector which automatically halts or checks the flow of fluid through the connector when it is disassembled. The automatic checking of fluid flow not only serves an important safety function by preventing the leaking of potentially dangerous fluids from the pipes but also facilitates efficiently carrying out many processes in various industries. The composite materials fabrication industry is one such industry which would benefit from having a connector which automatically checks the flow of fluid when disassembled.
None of the above-mentioned devices provides a pipe connector which may be easily assembled and disassembled and which also maintains a leak proof seal while the device is cycled through a wide range of temperatures and pressures. Further, none of the devices discussed above provide a pipe connector which provides adequate protection from injury to the operator due to rapid release of residual pressure contained in the connector. Still further, none of the devices meet the needs of the rapidly expanding composite materials fabrication industry.
In view of the foregoing, it would be an advancement in the art to provide a pipe union assembly which may be repeatedly used at very low temperatures and also at very high temperatures. It would also be an advancement to provide a pipe union assembly which maintains a fluid tight seal even when subjected to wide thermal cycles i.e., subjected to temperatures that greatly vary from the ambient temperature at the time of assembly.
It would be another welcome advancement in the art to provide a pipe union assembly which may be easily assembled without requiring cumbersome tools and which may be hand tightened and still be cycled through temperature and pressure changes without requiring subsequent adjustment.
It would also be an advancement in the art to provide a pipe union assembly which may be subjected to extreme internal pressures and still maintain a fluid-tight seal. Still another advancement would be to provide a pipe union incorporating a structure to allow release of residual pressure from the union without causing harm to the person disassembling the union.
It would be another advancement in the art to provide a pipe union assembly which could be reused many times without repair or modification subsequent to each use. It would be a still further advancement in the art to provide a pipe union assembly which automatically halts the flow of fluid from the pipe whenever the pipe union is disassembled.